According to the current wafer level packaging technology, a whole wafer is tested and packaged, and is cut to obtain separate finished chips. The wafer level packaging technology gradually replaces the wire bonding packaging technology, and becomes the mainstream packaging technology.
Image sensors are generally packaged using the wafer level packaging technology. FIG. 1 shows a conventional package for an image sensing chip, which includes an image sensing chip 10 and a protective cover plate 20. An image sensing region 12 and a contact pad 14 are arranged on a first surface of the image sensing chip, the protective cover plate 20 is arranged above the image sensing region 12 for protecting the image sensing region. The protective cover plate 20 generally includes a glass substrate 22 and a support structure 24 on the glass substrate 22, where a cavity is formed by the support structure 24. After the support structure 24 is bonded to the first surface where the image sensing region is located, the image sensing region 12 is located in the cavity and is protected. A guide hole extending to the contact pad 14 and a solder bump 22 electrically connected with the guide hole are arranged on a second surface of the image sensing chip for external electrical connection. The guide hole includes an insulation layer 16, an electrical connection layer 18 and a solder mask 20 which are arranged in a through hole and on the second surface on two sides of the through hole. The solder bump 22 is formed on the electrical connection layer 18 on a side of the through hole, for enabling external electrical connection of the contact pad.
However, in this structure, the electrical connection layer 18 is arranged between the solder mask 20 and the insulation layer 16 which is generally made of an organic material. The solder mask 20 and the insulation layer 16 have great thermal expansion coefficients, and are subject to expansion in a subsequent reliability test due to temperature variations, by which the electrical connection layer is compressed, and is prone to defects of virtual connection or even break.